Attachment F - Geotechnical Report

                              PROPOSED COMMERCIAL & RESIDENTIAL DEVELOPMENT
                              30-32 DOONELLA ST, TEWANTIN

Any permanent batters must be protected from erosion (e.g. with landscaping and geosynthetic erosion
matting).
Any excavations required adjacent to existing structures, will need to be specifically designed to ensure that
the structures are not adversely affected (refer Text Figure 6 in Section 6.2.2).

6.1.5        Filling
Any structural fill placed on this site must be compacted at moisture contents within the range of ±2% of
optimum moisture content for Standard Compaction. Fill particles greater than 100 mm must be excluded.
Fill should be placed in maximum 250 mm thick (loose thickness) layers and be compacted by repeated
rolling to achieve a dry density ratio of at least 98% of the maximum Dry Density Ratio (Standard
Compaction method), or 75% of the Dry Density Index for cohesionless fills (e.g. sands).

Confirmatory compaction testing must be carried out at regular intervals. Details for inspection and testing of
fill are given in Australian Standard AS 3798-2007 Guidelines on Earthworks for Commercial and Residential
Developments.

6.1.6        Material Suitability for Re-Use
Materials excavated from the basement area are expected to comprise predominantly medium to high
plasticity silty clays. These materials, where free of deleterious matter (e.g. vegetation), should be suitable
for placement as structural fill subject to appropriate moisture control. If placed as controlled fill under a
building pad, it should be noted that the equivalent site classification would likely be at least H1 per AS2870.

6.2       Building Foundations
6.2.1        Indicative Site Classification
Site classifications for residential footing design are assessed in accordance with AS 2870-2011 Residential
Slabs and Footings and depend on the depth of cut / fill undertaken at a site, variations in the natural soil
depths, and the reactivity of the in situ soil / rock and any imported fill materials. It should be noted that the
proposed works are outside of the scope of AS2870 and the applicability of the AS2870 classification to the
footing design must be assessed by the structural engineer.

Due to the presence of fill to depths of up to 0.75 m, the site is initially classified Class P in accordance with
AS2870. However, based upon the natural soil profiles encountered in the boreholes, the site could be
reclassified as equivalent to Class M if the fill was removed. Ground surface movements of between 20 mm
and 30 mm are estimated due to seasonal moisture content variation.

It should be noted that the predicted order of movement is based on the existing soil profile (i.e. no cutting or
filling), and moisture content changes within soils due to normal seasonal moisture variations only.

6.2.2        Footing Design
Conventional high level strip and pad footings founded within the very stiff (or stiffer) natural clays may be
designed to support the proposed building walls and columns, adopting an allowable bearing capacity of
250 kPa. Should greater load carrying capacity be required, deeper bored piles founded within the very stiff
(or stiffer) clay could be adopted.

Subject to design and construction in accordance with the above recommendations, settlements are
expected to be within building serviceability limits (less than 25 mm).

If any subsurface conditions encountered during construction are found to differ from those noted in the
geotechnical investigation, Tectonic should be notified immediately and an inspection carried out to
determine if changes to footing design are required.

All footings should found such that they are not adversely affected by any adjacent excavations, batter
slopes, trenches, or retaining walls that are not designed to support loads. To minimise the potential for any
adverse interaction effects, footings should found at least below a plane extending 1 m horizontally from the
base of trenches/excavations/retaining walls, then rising up at 1V:1H. This requirement is illustrated in Text
Figure 6 on the following page.


22 June 2018
Report No. 18151-001-Rev0                                8